The invention relates to an image processing method for extracting a thread-like structure represented on a background in a noisy digital image. The invention relates in particular to an image processing method for extracting the points representing a catheter guide-wire in an X-ray fluoroscopy medical image. The invention also relates to an X-ray apparatus having means for image processing.
The invention is applied in the manufacture of X-ray apparatus.
An image processing method for extracting a catheter guide-wire is already known from U.S. Pat. No. 5,289,373 5 (Zarge et al.). This patent relates to a method and an apparatus for the real-time tracking of a catheter guide-wire in fluoroscopy images during interventional radiological procedures. Such a method includes three main steps:
a pixel-wise extraction step for determining whether or not each pixel should be labeled as a possible guide-wire point so as to form an image called binary peak image,
a chain model construction step followed by an identification of a guide-wire model as the most promising path among previously determined chains, and
a step for the superimposition of the guide-wire model onto the live fluoroscopic images.
The first step is an iconic process that thoroughly exploits the outputs of several first and second order linear operators. The second step is non-iconic. It relates to morphological operations and to chain and tree oriented methods.
It is an object of the present invention to provide a method which can be carried out in real time, with a substantial gain in speed with respect to the prior art method described above, together with a higher sensitivity and selectivity, while using processing means with a speed of the kind presently used in the state of the art.
This aim is realized by a processing method for extracting a thread-like structure represented on the background in a noisy digital image, i.e., an original image, in which original image data is acquired and reduced using a transformation operation so as to provide a reduced image. The reduced image is processed by selecting the most probable locations of guide-wire points by selecting, at each point, the direction of the guide-wire which best matches one of several predetermined regularly oriented directions and by probing the contrast around and along in the selected directions. Then, reverting back to the original image, the contrast around the selected locations previously determined in the reduced image is probed and the point(s) which satisfy a contrast condition in the original image is/are extracted. The points which also satisfy a connectivity criterion in the reduced image are connected and extracted in the original image as guide-wire points of the original image.
An X-ray apparatus with means for carrying out the above processing methods in accordance with the invention also includes a display including a screen for displaying the medical digital images and the processed medical digital images.